Structural studies of excimer laser-induced percolative phase transition on polyimide thin film surfaces

The behavior of electrical conductivity for excimer laser irradiated polyim ide films in the vicinity of the critical number of laser shots was describ ed by three-dimensional percolative phase transition model. It is: found th at electrical conductivity changed more rapidly than that predicted by the percolation model. Thus, the change in microstructure with increasing numbe r of laser shots was analyzed by FT-IR Raman spectrometry and laser desorpt ion time-of-flight mass spectrometry. It is demonstrated that not only the number but also the average size of graphite particles on the irradiated po lyimide film surfaces increased with increasing number of laser shots. Thes e results were helpful to better understand the critical change in electric al conductivity on the irradiated polyimide film surfaces. (C) 2001 Elsevie r Science B.V. All rights reserved.